Hard coating and cutting tool using same

Abstract

To achieve a hard coating film or the like stably exerting high performance under broad processing conditions.SOLUTION: A hard coating film 12 has a structure in which A layer (A1-An) consisting of AlxCr1-xN and B layer (B1-Bn) consisting of Ti1-ySiyN are alternately laminated. The thickness of C layer is 7nm or more but 18nm or less when a set of A layer and B layer in which the A layer and the B layer are alternately laminated is defined as C layer (C1-Cn). The total thickness of C layers is 1 μm or more but 6 μm or less, and the thickness of A layer and that of B layer are less than 10nm, respectively (here, x is 0.6 or more but 0.7 or less, and y is more than 0.05 but less than 0.08).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hard coating and a cutting tool using the same. [Background technology]

[0002] Cutting tools used to process metal materials such as steel are subject to high hardness, so during cutting, the cutting tool is subjected to large impacts and may be exposed to high temperatures of over 800°C. Therefore, the surface of the cutting tool is usually coated to improve the wear resistance, heat resistance, etc. of the cutting tool.

[0003] The coating is performed by depositing a nitride of titanium, chromium, etc. onto a substrate such as high-speed steel, cemented carbide, etc. to form a thin film. Various methods have been proposed to improve the wear resistance, etc.

[0004] For example, Patent Document 1 discloses at least one (Al y Cr 1-y ) X layer (0.2≦y≦0.7), and / or one (Ti z Si 1-z )X layer (0.01≦z≦0.3), followed by one (AlCrTiSi)X mixed layer, then one (Ti z Si 1-z )X layer, then another (AlCrTiSi)X mixed layer, then another (Al y Cr 1-y ) X layers, where X is, for example, N. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-176837 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, Al in the hard substance layer y Cr 1-y N layer and Ti z Si 1-z It is described that an optimum thickness of the N layer is necessary to improve the life (

[0016] of Patent Document 1). y Cr 1-y The N layer is 75 to 200 nm, preferably 120 to 170 nm, and the Ti z Si 1-z The thickness of the N layer is set to 50 to 150 nm, preferably 70 to 120 nm.

[0007] AlCrN and TiSiN are materials commonly used for coating cutting tools. AlCrN has the advantage of excellent chipping resistance at low temperatures, but the disadvantage of reduced hardness and strength at high temperatures due to the loss of N. TiSiN also has the advantage of excellent wear resistance and being suitable for high-speed cutting operations, but the disadvantage of being hard and brittle. Therefore, hard coatings containing AlCrN and TiSiN are required to possess both of these advantages while avoiding the above disadvantages.

[0008] The hard substance layer described in Patent Document 1 includes the mixed layer and Al y Cr 1-y N layer and Ti z Si 1-z Since the N layer is thick, it is highly likely that it will exhibit the average properties of AlCrN and TiSiN or that one of the above-mentioned drawbacks will be apparent. Therefore, there is room for improvement in terms of the hard substance layer's ability to stably exhibit high performance under a wide range of processing conditions.

[0009] Furthermore, other conventional hard coatings have not been able to avoid the problem of the defects of either AlCrN or TiSiN being exposed, and as a result, cutting tools coated with these hard coatings have insufficient properties such as hardness, heat resistance, wear resistance, and chipping resistance, resulting in a short life, particularly under severe cutting conditions.

[0010] Therefore, an object of one aspect of the present invention is to provide a hard coating that combines the advantages of AlCrN and TiSiN and exhibits stable, high performance under a wide range of machining conditions, and a cutting tool using the same. [Means for solving the problem]

[0011] The present inventors have investigated the composition and structure of a hard coating that combines the advantages of AlCrN and TiSiN, and have discovered that by using specific compositions of AlCrN and TiSiN and forming specific laminated structures of AlCrN layers and TiSiN layers, it is possible to realize a hard coating that exhibits stable, high performance under a wide range of processing conditions, leading to the invention.

[0012] In order to solve the above problems, a hard coating according to one aspect of the present invention comprises Al x Cr 1-x The A layer is made up of N and the Ti 1-y Si y When a combination of the A layer and the B layer alternately constitutes a C layer, the thickness of the C layer is 7 nm or more and 18 nm or less, the total thickness of the C layer is 1 μm or more and 6 μm or less, and the thicknesses of the A layer and the B layer are each less than 10 nm (where x is 0.6 or more and 0.7 or less, and y is more than 0.05 and less than 0.08). [Effects of the Invention]

[0013] According to one aspect of the present invention, it is possible to provide a hard coating that combines the advantages of AlCrN and TiSiN and exhibits stable, high performance under a wide range of machining conditions, and a cutting tool using the same. That is, it is possible to provide a hard coating that has excellent wear resistance, heat resistance, and chipping resistance, as well as excellent film strength. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a longitudinal sectional view schematically showing the structure of the surface of a cutting tool provided with a hard coating according to an embodiment of the present invention. [Figure 2] 1 is a vertical cross-sectional view schematically showing an example of the structure of an arc evaporation device. [Figure 3] FIG. 3 is a top view of the arc evaporation device shown in FIG. 2 when observed vertically from above. [Figure 4] The X-ray diffraction patterns are shown below, obtained by subjecting two types of cutting tools (sample 1 and sample 2) provided with a hard coating in which AlCrN and TiSiN are laminated together, to X-ray diffraction. [Figure 5] FIG. 5 is an enlarged view of the vicinity of 2θ=34 to 40° in FIG. [Figure 6] Three types of cutting tools (samples 3 to 5) provided with hard coatings in which AlCrN and TiSiN are laminated were subjected to X-ray diffraction, and the X-ray diffraction patterns were obtained. [Figure 7] FIG. 7 is an enlarged view of the vicinity of 2θ=34 to 40° in FIG. [Figure 8] The hard coating of one of the cutting tools obtained in the examples was observed with a scanning transmission electron microscope (STEM), and the results are shown below. [Figure 9] This is the result of observing the hard coating shown in the left image of Figure 8 at a magnification of 1,000,000 times. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. In this specification, unless otherwise specified, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B."

[0016] [Embodiment 1: Hard Coating] The hard coating according to one embodiment of the present invention is Al x Cr 1-x The A layer is made up of N and the Ti 1-y Si y When a combination of the A layer and the B layer alternately constitutes a C layer, the thickness of the C layer is 7 nm or more and 18 nm or less, the total thickness of the C layer is 1 μm or more and 6 μm or less, and the thicknesses of the A layer and the B layer are each less than 10 nm (where x is 0.6 or more and 0.7 or less, and y is more than 0.05 and less than 0.08). Fig. 1 is a longitudinal cross-sectional view showing a schematic view of the surface structure of a cutting tool provided with a hard coating according to one embodiment of the present invention. In the figure, 11 is a substrate, 12 is a hard coating, and 10 is a cutting tool. Fig. 1 shows a case where n layers of A and n layers of B are laminated, and the A layers are designated A1 to A2. n and the B layer is represented as B1~B n In the figure, "..." indicates the distance from A3 to B n-1 1 shows an embodiment in which the surface of the substrate 1 is covered with Layer A and Layer B is laminated on Layer A, but the embodiment is not limited to this, and the surface of the substrate 1 may be covered with Layer B and Layer A may be laminated on Layer B.

[0017] In FIG. 1, layers A and B are alternately stacked. A layer C (for example, C1, C2, and C in the figure) is a combination of the layers A and B that are alternately stacked. n ) has a thickness of 7 nm or more and 18 nm or less.

[0018] The "structure in which layers A and B are alternately laminated" refers to a structure in which, for example, the surface of layer A is in contact with the surface of layer B, and the surface of layer B opposite the surface in contact with layer A is in contact with the surface of another layer A, and this structure is repeated. In other words, this refers to a laminate structure in which a combination of a pair of layers A and B is a repeating unit. For example, the surface of layer A1 in the figure is in contact with the surface of layer B1 in the figure, and the surface of layer B1 that is not in contact with layer A1 is in contact with layer A2, and this structure is repeated.

[0019] The Al constituting the A layer x Cr 1-x As mentioned above, N has the advantage of being excellent in fracture resistance at low temperatures, but has the disadvantage of decreasing hardness and strength at high temperatures due to the detachment of N. In addition, Ti constituting the B layer 1-y Si y N has the advantages of being highly wear-resistant and suitable for high-speed cutting work, but has the disadvantage of being hard and brittle.

[0020] By making the C layer as thin as 7 nm or more and 18 nm or less, it is possible to realize a hard coating that brings out only the advantages and does not bring out the disadvantages. This point will be explained below.

[0021] By setting the thickness of the C layer to 7 nm or more and 18 nm or less, in the hard coating, one A layer is sandwiched between two B layers with the thin C layer stacked. Since one A layer is sandwiched between two B layers, the only exposed surface of the A layer is the side. Because the C layer is thin, the thickness of the side is very thin. Therefore, the Al of the A layer x Cr 1-x The N contained in Ti 1-y Si y N blocks shedding.

[0022] Furthermore, by setting the thickness of the C layer to 7 nm or more and 18 nm or less, in the hard coating, one B layer is sandwiched between two A layers with the thin C layer stacked. Since the C layer is a thin layer and one B layer is sandwiched between two A layers, Ti 1-y Si y The development of defects or cracks due to the defects of N is x Cr 1-x It is blocked by N.

[0023] Thus, in each C layer, Al x Cr 1-x N and Ti 1-y Si y The hard coating according to one embodiment of the present invention has a structure in which each C layer in which the appearance of the defects is prevented is stacked, and therefore the defects are not revealed in the hard coating as a whole, and only the advantages are revealed.

[0024] On the other hand, in the package structure described in Patent Document 1, for example, as mentioned above, the optimum layer thickness is Al y Cr 1-y The N layer is 75 to 200 nm, preferably 120 to 170 nm, and the Ti z Si 1-z The thickness of the N layer is set to 50 to 150 nm, preferably 70 to 120 nm.

[0025] In this configuration, the Al y Cr 1-y The N layer may not be able to prevent the N from falling off sufficiently, or Ti z Si 1-z It is not possible to sufficiently prevent the development of defects or cracks due to defects in the N layer. Furthermore, the hard substance layer described in Patent Document 1 has multiple mixed layers, but the mixed layers either exhibit the average properties of AlCrN and TiSiN, or become layers in which defects inherent in either AlCrN or TiSiN are exposed.

[0026] In one embodiment of the present invention, the thickness of the C layer is more preferably 9 nm or more and 17 nm or less, and even more preferably 11 nm or more and 15 nm or less. x Cr 1-x N sheds and Ti 1-y Si y The development of defects or cracks caused by the above-mentioned drawbacks of N can be more efficiently prevented.

[0027] In the hard coating according to one embodiment of the present invention, the thickness of each of the A layer and the B layer is less than 10 nm.

[0028] In order for the hard coating to exhibit excellent wear resistance, heat resistance, chipping resistance, and high film strength, it is preferable that the layers A and B are contained in a balanced manner in the layer C. Therefore, the ratio of the thickness of the layers A to the thickness of the layers B in the layer C is preferably 2:3 to 3:2, more preferably 4:5 to 5:4, and most preferably 6:7.

[0029] The total thickness of the C layers is 1 μm or more and 6 μm or less. That is, the hard coating has a structure in which a great number of C layers are laminated, i.e., an ultra-multilayer structure.

[0030] The hard coating is Al x Cr 1-x N and Ti 1-y Si y The hard coating has an ultra-multilayered structure in which a structure capable of bringing out only the advantages of N is repeatedly laminated. Therefore, the hard coating has excellent wear resistance, heat resistance, and chipping resistance, as well as excellent film strength. Because the hard coating has these excellent properties, it can be used to process a variety of materials, from soft to hard (for example, hardness of 20 to 60 HRC), and can be adapted to a variety of processing conditions.

[0031] Therefore, it is possible to stably exhibit high performance under a wide range of processing conditions, including conditions corresponding to processing temperatures ranging from low to high, and conditions corresponding to processing methods such as wet processing, dry processing, and high-speed cutting.

[0032] The hard coating can be particularly preferably used in gear cutting. Gear cutting is a process for cutting steel or the like into a complex gear shape. Machining the large cut portions of the gear shape places a large load on the cutting tool blade. Machining the small cut portions of the gear shape places a load only on the cutting edge of the cutting tool. Therefore, hard coatings used in gear cutting are particularly required to have wear resistance, heat resistance, chipping resistance, and high strength.

[0033] A hard coating that is weak in any one of wear resistance, heat resistance, chipping resistance, and strength cannot withstand harsh cutting conditions at the weak portions, resulting in a shortened cutting tool life and reduced processing efficiency. As described above, the hard coating according to one embodiment of the present invention has excellent wear resistance, heat resistance, and chipping resistance, as well as excellent film strength. Therefore, it can be suitably used for gear cutting. Of course, this is not a limitation, and the hard coating can also be suitably used for other processing applications. For example, it can be suitably used as a hard coating for cemented carbide blades, drills, end mills, etc., as described below.

[0034] The total thickness of the C layer is more preferably 2 μm or more and 4.5 μm or less.

[0035] The hard coating may have a structure in which an A layer that does not form the C layer is laminated next to a B layer that forms the C layer at the end of the laminate structure. For example, in the case of B shown in FIG. n Similarly, the hard coating may have an embodiment in which a layer B that does not form the layer C is laminated on an end of the layered structure, followed by a layer A that forms the layer C.

[0036] In this case, the structure is such that the A layer is sandwiched between two B layers, or the B layer is sandwiched between two A layers, so the Al x Cr 1-x N Yobi Ti 1-y Si y It can only bring out the strengths that N possesses.

[0037] The Al x Cr 1-x The x of N is 0.6 or more and 0.7 or less, and the Ti 1-y Si y The y of N is more than 0.05 and less than 0.08. x Cr 1-x The A layer is made up of N and the Ti 1-y Si y The requirements that the thickness of the C layer is 7 nm or more and 18 nm or less, and the total thickness of the C layers is 1 μm or more and 6 μm or less are satisfied, and the hard coating can thereby exhibit the excellent abrasion resistance and the like described above.

[0038] Al wherein x is 0.6 or more and 0.7 or less x Cr 1-x N can be adjusted by controlling the composition of the AlCr target raw material, the N pressure during C layer formation, the bias voltage, etc. Also, Ti where y is more than 0.05 and less than 0.08 1-y Si y Similarly, N can be adjusted by controlling the composition of the TiSi target raw material, the N2 pressure during C layer formation, the bias voltage, and the like.

[0039] In addition, the prepared Al x Cr 1-x The x of N is 0.6 or more and 0.7 or less, and Ti 1-y Si y The fact that y of N is greater than 0.05 and less than 0.08 can be confirmed by an EDX analyzer attached to an SEM and / or TEM.

[0040] The hard coating according to one embodiment of the present invention can be produced by, for example, arc ion plating of a substrate, using a vacuum deposition device such as an arc evaporation device (manufactured by Nippon ITF Corporation) equipped with a Stir-One evaporation source.

[0041] Fig. 2 is a longitudinal cross-sectional view showing a schematic example of the structure of the arc evaporation device. Fig. 3 is a top view of the arc evaporation device shown in Fig. 2 when viewed vertically from above. In the figure, 20 denotes the arc evaporation device, 21 denotes a Cr evaporation source, and 22 denotes an Al evaporation source. x Cr 1-x Arc evaporation source, 23 is Ti 1-y Si y The arc evaporation source 24 is a rotary table, 25 is a small table, 26 is an arc power supply, and 27 is a bias power supply. The small table 25 is connected to the rotary table 24 by gears, and therefore rotates on its axis as the rotary table 24 rotates. The gear ratio between the rotary table 24 and the small table 25 is preferably a value greater than 6 and not an integer, assuming that the number of gears on the small table 25 is 1.

[0042] The interior of the arc evaporation apparatus 20 is a vacuum chamber. An example of a method for producing a cutting tool by coating a substrate with a hard coating according to one embodiment of the present invention using the arc evaporation apparatus 20 will be described below. This method is also used in the examples described below.

[0043] First, the rotary table 24 with the substrate 11 placed on the small table 25 is placed inside the arc evaporation apparatus 20 (inside the furnace).

[0044] Next, the interior of the arc evaporation apparatus 20 is evacuated to a specified degree of vacuum, and the substrate 11 is heated by a heater (not shown) until it reaches 400°C. Subsequently, as shown in FIG. 3, argon gas is introduced into the furnace, and the pressure inside the furnace is set to 1 Pa. Thereafter, a bias voltage of -900 V is applied to the substrate 11 by the bias power supply 27, and the substrate 11 is etched by argon ions. After the argon gas is exhausted, nitrogen gas is introduced into the furnace, and the internal pressure is set to 4 Pa, as shown in FIG. 3.

[0045] Next, the arc power supply 26 is operated to emit Al from the arc evaporation source 22. x Cr 1-x Arc discharge was performed at 150 A, and Ti was evaporated from the arc evaporation source 23. 1-y Si y Arc discharge is performed at 140A. x Cr 1-x and Ti 1-y Si y is evaporated into a nitrogen gas atmosphere.

[0046] The rotary table 24 is rotating, and the substrate 11 is rotating on its axis. Therefore, when the substrate 11 faces the arc evaporation source 22, the Al x Cr 1-x is deposited on the substrate 11 and simultaneously combines with the nitrogen gas to form Al x Cr 1-x A film of N is formed on the surface of the substrate 11 .

[0047] On the other hand, when the substrate 11 faces the arc evaporation source 23, Ti 1-y Si y is deposited on the substrate 11 and simultaneously combines with the nitrogen gas, forming Ti 1-y Si y A film of N is formed on the surface of the substrate 11 .

[0048] By repeating the above operations, a hard coating according to one embodiment of the present invention can be formed on the surface of the substrate 11. At this time, by applying a bias voltage to the substrate 11, ions of the evaporated metal elements (Ti, Si, Al, Cr) are strongly attracted to the substrate 11, which densifies the film and adjusts the strength and residual stress of the hard coating.

[0049] The thickness of the C layer and the total thickness of the C layers can be controlled to 7 nm or more and 18 nm or less and 1 μm or more and 6 μm or less by adjusting the arc current and the rotation speed of the turntable 24, respectively.

[0050] After forming a hard coating having a predetermined C layer thickness and the total thickness of the C layers, the temperature inside the furnace is cooled to 200°C or less, the furnace is opened to the atmosphere, and the manufactured cutting tool is removed.

[0051] The hard coating thus produced can be confirmed to have a predetermined structure by observing the longitudinal section of the hard coating using, for example, a scanning transmission electron microscope. The predetermined structure is a structure in which layers A and B are alternately laminated, the thickness of the layer C is 7 nm to 18 nm, and the total thickness of the layers C is 1 μm to 6 μm. For example, based on the observation results shown in FIG. 9 (described later), the thickness of layer C can be calculated by measuring the total thickness of 10 to 20 consecutive layers and dividing by the number of combinations of layers A and B. The thicknesses of layers A and B can be determined by measuring the thickness of each of approximately 5 to 10 layers and calculating the average value.

[0052] In the hard coating according to one embodiment of the present invention, the ratio (A / B) of the intensity of the sub-peak (A) to the intensity of the main peak (B) in the X-ray diffraction pattern of the hard coating is preferably 0.4 or more and 0.75 or less.

[0053] The main peak is a peak of the crystals of Layer A and Layer B. Sub-peaks are peaks that appear near the main peak (near the low-angle and high-angle sides of the main peak in the X-ray diffraction pattern) and are peaks that are caused by the super multi-layer structure. The ratio is an indicator of whether the hard coating has the super multi-layer structure.

[0054] The X-ray diffraction pattern can be obtained by, for example, performing X-ray diffraction measurement of the hard coating by the θ-2θ method under the following conditions: Measurement device: Bruker AXS X-ray diffractometer D8 DISCOVER, X-ray source: Cu-Kα, tube voltage: 40 kV, tube current: 40 mA, slit width: 0.5°, one-dimensional detector, step: 0.02°, accumulation time: 0.6 seconds, scan range 2θ = 30 to 50°. A method for determining the ratio (A / B) will be described below.

[0055] Figure 4 shows the X-ray diffraction patterns obtained by X-ray diffraction of two types of cutting tools (sample 1 and sample 2) equipped with a hard coating in which AlCrN and TiSiN are laminated. Figure 5 is an enlarged view of Figure 4 in the vicinity of 2θ=34 to 40°.

[0056] First, as shown in Figure 5, a line was drawn connecting the intensity at 2θ = 34° and the intensity at 2θ = 39° for each of Sample 1 and Sample 2. Next, the differences between the line and each of the following peaks (subpeak 1 near 36°, the peak of the TiSiN(111) plane near 36.5°, the peak of the AlCrN(111) plane near 37.3°, and subpeak 2 near 37.8°) (the lengths of the vertical lines shown in the figure) were defined as the intensities I1, I2, I3, and I4 of each peak. The ratio (A / B) was then calculated as (I1 + I4) / (I2 + I3). The results of calculating the ratios for Sample 1 and Sample 2 shown in Figure 4 are shown in Table 1.

[0057] [Table 1]

[0058] Figure 6 shows the X-ray diffraction patterns obtained by X-ray diffraction of three types of cutting tools (samples 3 to 5) equipped with hard coatings in which AlCrN and TiSiN are laminated. Figure 7 is an enlarged view of the vicinity of 2θ=34 to 40° in Figure 6. The straight line shown in Figure 7 was drawn, and the ratio (A / B) was determined using the same method as described for samples 1 and 2. The results are shown in Table 2.

[0059] [Table 2]

[0060] The ratio is more preferably 0.45 or more and 0.72 or less, and even more preferably 0.5 or more and 0.55 or less, which can be used as a more useful indicator that the hard coating has the ultra-multilayer structure.

[0061] The hard coating according to one embodiment of the present invention preferably has a compressive stress of -0.5 GPa or more and -4.0 GPa or less. With this configuration, the hard coating has high resistance to impact and is not easily broken. From this viewpoint, the compressive stress is more preferably -1 GPa or more and -3 GPa or less, and even more preferably -1.5 GPa or more and -2.5 GPa or less. The compressive stress can be measured, for example, by sin sigma using X-ray diffraction. 2 It can be measured by the φ method or a measurement method based on the Stoney equation using a test piece.

[0062] The hard coating according to one embodiment of the present invention preferably has a surface roughness Ra of 0.03 μm or more and 0.18 μm or less. If the surface roughness Ra exceeds 0.18 μm, irregularities will occur not only on the surface but also inside the hard coating, making it difficult to form the ultra-multilayer structure. In addition, it will be difficult to find the subpeaks in the X-ray diffraction pattern. The lower the lower limit of the surface roughness Ra, the better, but the practical lower limit is 0.03 μm.

[0063] Therefore, the surface roughness Ra of the hard coating of 0.03 μm or more and 0.18 μm or less is an indicator that the hard coating according to one embodiment of the present invention has the ultra-multilayer structure. Furthermore, with this configuration, it can be said that the surface smoothness of the hard coating is extremely high.

[0064] Therefore, the hard coating can stably exhibit high performance under a wide range of processing conditions, and because it has high smoothness, it can improve the quality of the processed object.

[0065] From this viewpoint, the surface roughness Ra of the hard coating is more preferably 0.06 μm or more and 0.15 μm or less, and even more preferably 0.08 μm or more and 0.14 μm or less.

[0066] The surface roughness Ra can be measured, for example, by the following method: a surface of a test piece having a sufficiently small surface roughness Ra is coated with the hard coating by ion plating or the like, and the surface roughness Ra of the coated test piece is measured.

[0067] The test piece may be, for example, a test piece having a surface roughness Ra of 0.01 μm or less. Because the surface roughness Ra of the test piece is sufficiently small, the surface roughness Ra of the test piece coated with the hard coating can be considered to be the surface roughness Ra of the hard coating.

[0068] Another method for measuring the surface roughness Ra is, for example, the following method. That is, a longitudinal section of a cutting tool having a substrate surface coated by ion plating or the like is prepared. Next, the shape of the interface between the hard coating and the substrate is extracted as a profile of the substrate surface using a scanning electron microscope, and Ra is calculated according to the Ra calculation method. Similarly, the shape of the hard coating surface is extracted as a film surface profile, and Ra is calculated according to the Ra calculation method. The value obtained by subtracting the Ra of the substrate surface from the Ra of the film surface is defined as the Ra of the hard coating.

[0069] The Ra can be measured using, for example, a surface roughness measuring instrument manufactured by DEKTAK.

[0070] The hard coating according to one embodiment of the present invention preferably has a nanoindentation hardness of 35 GPa or more and 40 GPa or less.

[0071] According to this configuration, the hard coating has sufficient strength and is therefore resistant to machining of high-hardness materials, which can contribute to improving the sharpness of cutting tools and the ability to remove chips.

[0072] The nanoindentation hardness can be measured, for example, using a nanoindenter ENT-1100 manufactured by Elionix as a measuring device, and applying a load of 2 g to the hard coating on the surface of the cutting tool using a Berkovich indenter.

[0073] [Embodiment 2: Cutting Tool] A cutting tool according to one embodiment of the present invention comprises a substrate and a hard coating covering the surface of the substrate, the hard coating being the hard coating according to one embodiment of the present invention.

[0074] Examples of the cutting tools include gear cutting tools such as hobs, cemented carbide blades, broaches, rolling flat dies, shaving cutters, and pinion cutters; drills; end mills; threading tools such as taps, threading dies, chasers, thread milling cutters, and thread rolling dies; indexable tools such as inserts; and wear-resistant tools such as drawing tools, rolling tools, shearing tools, forging tools, molds, tools for electronic-related components, and machine mounting parts.

[0075] The hard coating according to one embodiment of the present invention has a good balance of all of the properties, namely, wear resistance, heat resistance, fracture resistance, and high hardness, and therefore the cutting tool can be used with a wide range of workpiece materials, for example, with a hardness of 20 to 60 HRC.

[0076] In recent years, the operating conditions for gear cutting tools have become increasingly high-speed and dry, increasing the impact on the cutting edges and the temperature of the cutting edges. In addition, gear cutting tools have multiple cutting edges, such as hobs, and due to the nature of gear cutting, the load on each cutting edge varies.

[0077] Therefore, a cutting tool having a hard coating that is weak in any of the above characteristics cannot be used stably under the above conditions. Furthermore, such a cutting tool cannot adapt to loads that vary from cutting edge to cutting edge, and therefore cannot be used as a gear cutting tool. The cutting tool according to one embodiment of the present invention has all of the above characteristics in a balanced manner, and therefore can operate stably under the above conditions. Furthermore, it can be suitably used as a gear cutting tool.

[0078] The cutting tool can be obtained by forming the hard coating on a substrate by a method such as arc ion plating. Other methods that can be used include sputtering methods such as HiPIMS (high power pulse sputtering), and vapor deposition.

[0079] The substrate may be made of high-speed steel, cemented carbide, etc. The cemented carbide may be made of WC-Co alloy, WC-TiC-Co alloy, WC-TaC-Co alloy, WC-TiC-TaC-Co alloy, WC-Ni alloy, WC-Ni-Cr alloy, etc.

[0080] 〔summary〕 The present invention includes the following aspects. <1> Al x Cr 1-x The A layer is made up of N and the Ti 1-y Si y and N-based B layers are alternately laminated, When a combination of the A layer and the B layer alternately stacked is referred to as a C layer, the thickness of the C layer is 7 nm or more and 18 nm or less, the total thickness of the C layer is 1 μm or more and 6 μm or less, The hard coating, wherein the thickness of each of the A layer and the B layer is less than 10 nm.

[0081] (wherein, x is equal to or greater than 0.6 and equal to or less than 0.7, and y is greater than 0.05 and less than 0.08.) <2> In the X-ray diffraction pattern of the hard coating, the ratio (A / B) of the sub-peak intensity (A) to the main peak intensity (B) is 0.4 or more and 0.75 or less. <1> The hard coating according to claim 1. <3> The compressive stress is between -0.5GPa and -4.0GPa. <1> or <2> The hard coating according to claim 1. <4> The surface roughness Ra is 0.03 μm or more and 0.18 μm or less. <1> ~ <3> 10. The hard coating according to claim 9, wherein the hard coating is a film having a thickness of 100 nm or less. <5> The hard coating is provided on a surface of a substrate. <1> ~ <4> A cutting tool comprising the hard coating according to any one of the preceding items. <6> The cutting tool is a gear cutting tool. <5> The cutting tool according to claim 1.

[0082] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0083] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0084] Examples 1 to 13 (1) Manufacturing of a cutting tool provided with a hard coating according to one embodiment of the present invention Using the arc evaporation apparatus 20 shown in Figures 2 and 3, cutting tools with hard coatings according to one embodiment of the present invention were manufactured based on the method described above with reference to Figures 2 and 3. The substrates used were a high-speed steel hob; a 20 mm square, 2 mm thick high-speed steel test piece with a mirror-lapped surface (surface roughness Ra = 0.01 μm or less); and a cemented carbide test piece with a width of 10 mm, a length of 20 mm, and a thickness of 1 mm. In this example, a total of 13 hobs, each 80 mm in diameter and 150 mm in length, were manufactured. These were designated as cutting tools according to Examples 1 to 13.

[0085] When preparing the cutting tools according to Examples 1 to 13, the Al arc discharged from the arc evaporation source 22 x Cr 1-x The values ​​of x in the above formulas were 0.6 or more and 0.7 or less (see the "Al composition" column in Table 3). 1-y Si y The y values ​​of the respective hard coatings were more than 0.05 and less than 0.08 (see the "Si composition" column in Table 3). x Cr 1-x The composition ratio (atm%) of Al and Cr in the B layer (Ti N layer) 1-y Si y The composition ratios (atm %) of Ti and Si in the layer (layer consisting of N) are shown in Table 3. The thickness of the C layer, the film thickness of the hard coating (total thickness of the C layer), and the number of layers (sum of the number of A layers and the number of B layers) are also shown in Table 3.

[0086] For each example, the high-speed steel test pieces and cemented carbide test pieces were also subjected to the above method at the same time. The atm %, thickness of the C layer, total thickness of the C layer, and number of layers of the hard coatings formed on these test pieces were the same as those of the hard coatings obtained in the corresponding examples.

[0087] FIG. 8 shows the results of observing the longitudinal section of the hard coating of one of the cutting tools obtained in the examples with a scanning transmission electron microscope (STEM) (bright field image, magnification: 50,000 times).

[0088] FIG. 9 shows the results of observing the hard coating shown in FIG. 8 at a magnification of 1,000,000 times. As shown in FIG. 9, it can be seen that a regular layered structure is well formed. Based on the observation results such as those in FIG. 9, the thickness of layer C can be calculated by measuring the total thickness of 10 to 20 consecutive layers and dividing it by the number of combinations of layers A and B. For the hard coatings obtained in Examples 1 to 13 and Comparative Examples 1 to 4, the thickness of layer C was calculated based on the results of STEM observation. The total thickness of layer C was determined by measuring the total thickness of layer C observed by STEM.

[0089] (2) X-ray diffraction The hobs obtained in Examples 1 to 13 were subjected to X-ray diffraction and measured using the θ-2θ method under the following conditions: Measurement equipment: Bruker AXS X-ray diffractometer D8 DISCOVER; X-ray source: Cu-Kα; tube voltage: 40 kV; tube current: 40 mA; slit width: 0.5°; step: 0.02°; integration time: 0.6 seconds; scan range 2θ = 30 to 50°. Next, from the X-ray diffraction pattern obtained for each hob, the ratio (A / B) of the subpeak intensity (A) to the main peak intensity (B) was calculated based on the method described above and performed with reference to Figures 3 to 6. The results are shown in Table 3.

[0090] (3) Measurement of surface roughness Ra of hard coating The surface roughness Ra of the surface-coated test pieces made of high-speed steel obtained at the same time as Examples 1 to 13 was measured using a surface roughness measuring instrument made by DEKTAK, and was taken as the surface roughness Ra of the hard coating. The results are shown in Table 3.

[0091] (4) Nanoindentation hardness measurement of hard coating For the hobs obtained in Examples 1 to 13, a nanoindentation hardness of the hard coating was measured using a nanoindenter ENT-1100 manufactured by Elionix and a Berkovich indenter by applying a load of 2 g to the hard coating on the surface of each cutting tool. The results are shown in Table 3.

[0092] (5) Measurement of compressive stress The warpage of the surface-coated test pieces made of cemented carbide obtained in Examples 1 to 13 was measured using a surface roughness measuring instrument manufactured by DEKTAK, and the compressive stress was measured based on the Stoney equation. The results are shown in Table 3.

[0093] (6) Cutting test 1 The hobs obtained in Examples 1 to 7 were subjected to dry cutting of SCM415 gears under the conditions of a cutting speed (V) of 180 m / min, a feed of 2.5 mm / rev., and climb cut. After cutting 100 gears, the wear width of the cutting edge was checked under a microscope. The results were evaluated based on the number of cuts until the wear width exceeded 0.2 mm or the cutting edge was chipped. The results are shown in Table 3.

[0094] (7) Cutting test 2 The hobs obtained in Examples 8 to 13 were subjected to dry cutting of SCR420H gears under the conditions of a cutting speed (V) of 160 m / min, a feed rate of 1.5 mm / rev., and climb cut. The wear width of the cutting edge was checked under a microscope every 100 pieces cut. The results were evaluated based on the number of cuts until the wear width exceeded 0.2 mm or the cutting edge was chipped. The results are shown in Table 3.

[0095] Comparative Examples 1 to 4 Layers A and B having the compositions shown in Table 3 were formed on a high-speed steel hob, a 20 mm square, 2 mm thick high-speed steel test piece with a mirror-lapped surface, and a cemented carbide test piece having a width of 10 mm, a length of 20 mm, and a thickness of 1 mm, by the same method as in Examples 1 to 13. As a result, hobs and test pieces having the thickness of layer C, the total thickness of layer C, and the number of layers shown in Table 3 were obtained.

[0096] When the cutting tools according to Comparative Examples 1 to 4 were prepared, the Al vaporized by arc discharge from the arc evaporation source 22 x Cr 1-x The x's were the values ​​shown in the "Al composition" column of Table 3. 1-y Si yThe y values ​​were the values ​​shown in the "Si composition" column of Table 3. In Comparative Examples 3 and 4, the arc current and the rotation speed of the turntable 25 were changed from those in Examples 1 to 13 and Comparative Examples 1 and 2, and the C layer thickness was set to less than 7 nm or more than 18 nm.

[0097] The hob was subjected to X-ray diffraction, measurement of the nanoindentation hardness of the hard coating, and cutting test 1 in the same manner as in Examples 1 to 13. In addition, the surface roughness Ra was measured using the surface-coated test piece made of high-speed steel, and the compressive stress was measured using the surface-coated test piece made of cemented carbide. The results are shown in Table 3.

[0098] [Table 3]

[0099] The "sub-peak intensity ratio" is the ratio (A / B) of the intensity of the sub-peak (A) to the intensity of the main peak (B) in the X-ray diffraction pattern of the hard coating, and the "film hardness" is the nanoindentation hardness of the hard coating.

[0100] In Comparative Example 1, the Si composition is 5.0 atm%, which does not exceed 5 atm%. In Comparative Example 2, the Si composition is 8.0 atm%, which does not exceed 8 atm%. In Comparative Example 3, the C layer thickness is 5 nm, which does not satisfy the requirement of 7 nm to 18 nm. In Comparative Example 4, the C layer thickness is 20 nm, which does not satisfy the requirement of 7 nm to 18 nm.

[0101] The hobs described in Comparative Examples 1 to 4 have the same sub-peak intensity ratios and surface roughness Ra as those of the Examples, but the results of Cutting Test 1 are clearly inferior to those of the Examples. This is thought to be because the requirements that the hard coating according to one embodiment of the present invention should have are not met.

[0102] On the other hand, the hobs described in Examples 1 to 13 all satisfied the Al composition, Cr composition, Ti composition, Si composition, C layer thickness, and total C layer thickness required for the hard coating according to one embodiment of the present invention. As a result, the results of the cutting test were very good.

[0103] As described above, the hard coating according to one embodiment of the present invention is x Cr 1-x The A layer is made up of N and the Ti 1-y Si y and a B layer made of N, which are alternately laminated together, and when a combination of the A layer and the B layer that are alternately laminated is called a C layer, the thickness of the C layer is 7 nm or more and 18 nm or less, the total thickness of the C layer is 1 μm or more and 6 μm or less, and the thicknesses of the A layer and the B layer are each less than 10 nm (where x is 0.6 or more and 0.7 or less, and y is more than 0.05 and less than 0.08)." By satisfying the requirements, it is possible to provide a hard coating that has excellent wear resistance, heat resistance, and chipping resistance, as well as excellent film strength. [Industrial Applicability]

[0104] The present invention can be suitably applied to cutting tools used under a wide range of machining conditions. [Explanation of symbols]

[0105] 10...cutting tools 11...Base material 12...hard coating A1~A n ···A layer B1~B n ···B layer C1~C n ...C layer 20. Arc evaporation device 21. Cr evaporation source 22···Al x Cr 1-x Arc evaporation source 23 Ti 1-y Si y Arc evaporation source 24 Rotating table 25. Small table 26 Arc Power Supply 27. Bias power supply

Claims

1. Al ｘ Cr １－ｘ A layer consisting of N and Ti １－ｙ Si ｙ and a B layer made of N, When a combination of the A layer and the B layer alternately stacked is referred to as a C layer, the thickness of the C layer is 7 nm or more and 18 nm or less, the total thickness of the C layer is 1 μm or more and 6 μm or less, the thickness of each of the A layer and the B layer is less than 10 nm; In an X-ray diffraction pattern, the ratio (A / B) of the sub-peak intensity (A) to the main peak intensity (B) is 0.4 or more and 0.75 or less. Hard coating. (wherein, x is 0.6 or more and 0.7 or less, and y is more than 0.05 and less than 0.08.)

2. 2. The hard coating according to claim 1, wherein the compressive stress is −0.5 GPa or more and −4.0 GPa or less.

3. 2. The hard coating according to claim 1, having a surface roughness Ra of 0.03 μm or more and 0.18 μm or less.

4. A cutting tool comprising a substrate and a hard coating covering a surface of the substrate, the hard coating being the hard coating according to any one of claims 1 to 3.

5. The cutting tool according to claim 4 , wherein the cutting tool is a gear cutting tool.

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